Various apparatus have been proposed for directing heated pressurized fluid streams, such as air or stream, into the surface of moving textile fabrics to alter the location of or modify the thermal properties of fibers or yarns therein and provide a pattern or visual surface change in such fabrics. Examples of such prior art equipment and methods of application of the pressurized fluid streams to a relatively moving material are disclosed in the following U.S. Pat. Nos: 2,110,118; 2,241,222; 2,563,259; 3,010,179; 3,403,862; 3,434,188; 3,585,098; 3,613,186.
It is believed that such prior art treatment devices as described in the aforementioned patents, because of the nature of the equipment disclosed, are not capable of producing precise, intricate, or well defined patterns of wide variety in the fabrics, but generally can only produce limited, relatively grossly defined patterns, or surface modifications of a random, non-defined nature in the materials. In utilizing high temperature pressurized streams of fluid, such as air, to impart visual surface patterns to textile fabrics containing thermoplastic materials by thermal modification of the same, it can be appreciated that highly precise control of stream pressure, temperature, and direction is required in all of the individual heated streams striking the fabric to obtain uniformity and preciseness in the resultant pattern formed in the fabric. In addition, there are ever present difficulties in regulating the flow of high temperature fluid streams by use of conventional valving systems to selectively cut the stream flow on or off in accordance with pattern control information.
More recently, apparatus has been developed for more precisely and accurately controlling and directing high temperature streams of pressurized fluid, such as air, against the surface of a relatively moving substrate material, such as a textile fabric containing thermoplastic yarns, to impart intricate patterns and surface changes thereto. Such apparatus includes an elongate pressurized heated air distributing manifold having a narrow elongate air discharge slot extending across the path of fabric movement in close proximity to the fabric surface. Located within the manifold is a shim plate having a notched edge which resides in the discharge slot to form parallel spaced discharge channels through which the heated pressurized air passes in narrow, precisely defined streams to impinge upon the adjacent surface of the fabric. Flow of the individual heated air streams from the channels is controlled by the use of pressurized cool air which is directed by individual cool air supply tubes communicating with each channel to direct cool air into each discharge channel at a generally right angle to its discharge axis to block the passage of heated air therethrough. Each cool air tube is provided with an individual valve and the valves are selectively cut on and off in response to signal information from a pattern source, such as a computer program, to allow the heated air streams to strike the moving fabric in selected areas and impart a pattern thereto by thermal modification of the yarns.
To maintain more uniform temperature in the individual heated air streams along the full length of the distributing manifold, pressurized air is supplied to the distributing manifold through a bank of individual electric heaters which communicate with the manifold at uniformly spaced locations along its length and are regulated to introduce heated air at the desired temperature along the full length of the manifold.
Although such apparatus as described above provides for high precise and intricate hot air patterning of substrate materials, it can be appreciated that the temperature and pressure of each of the individual pressurized streams of high temperature air striking the surface of the substrate material must be uniform across the full width of the substrate being treated, otherwise irregular patterning of the substrate occurs. For example, in treatment of textile pile fabrics containing thermoplastic pile yarns, the streams of heated air striking the pile yarns in selected areas of the fabric cause the yarns to thermally deform, longitudinally shrink, and compact into the pile surface, forming narrow, precisely defined grooves or recesses which provide a desired patterned appearance in the pile surface. If the temperature or pressure in any of the air streams across the width of the fabric varies significantly from the others, the resultant patterned groove or recess formed thereby will be more or less pronounced in the pattern and correspondingly detract from the appearance of the final product.
When pressurized cool air is employed to block selected of the heated air discharge channels of the manifold to produce a desired pattern, as in the aforementioned apparatus, there is a momentary cooling of the manifold housing around the heated air discharge channel blocked by the cool air, resulting in a slight temperature drop in adjacent heated air streams striking the fabric, and a reduced temperature in the heated air stream discharged from the channel after it is unblocked. When a large number of discharge channels across the manifold are simultaneously blocked by cool pressurized air, the cooling effect on the manifold housing becomes more pronounced. In addition, a pressure build-up of heated air can occur in the manifold itself, causing undesired temperature and pressure variations in the heated air streams during the patterning operation, and contributing to overheating of the heater elements.